What are the exiting and entering criteria in the performance testing?

We can start the performance testing of application during the design. After the execution of the performance testing, we collected the results and analyzed them to improve the performance. The performance tuning processed will be performed throughout the application development life cycle. Performance tuning is performed which is based on factors like release time of application and user requirements of application stability, reliability and scalability under load, stress and performance tolerance criteria. In some projects the end criteria is defined based on the client performance requirements defined for each section of the application. When product reaches to the expected level then that can be considered as the end criteria for performance testing.